To electrically test printed circuit mounted integrated circuits or other devices, termed hereinafter "units under test", or "UUTs", external test instrumentation is connected to the leads of the UUT via an electrical cable, typically ribbon type cable, and a conventional test clip of a type described in U.S. Pat. No. 3,914,007. The test clip comprises an array of contact pins located within parallel channels of a pair of molded support arms. The two arms, pivotally connected to each other, are spring biased closed to grip a UUT with the pins of the clip in electrical contact with the leads of the UUT. The contact pins extend outward somewhat from the tops of the test clip arms to enable access to the pins for electrical contact. A ribbon cable, which is a flat array of parallel, closely aligned wires, carries electrical test signals between the UUT and the external instrumentation. A conventional ribbon cable socket interconnects the individual wires of the cable and the test clip by slipping onto the contact pins extending out the tops of the two arms.
During a test, high frequency test signals are exchanged between the UUT and the external test instrumentation through the ribbon cable and test clip. BEcause the wires of the ribbon cable are immediately adjacent each other, however, there is electrical coupling or "crosstalk" between signal lines which tends to interfere with the reliability of the test. There accordingly exists a need to electrically isolate or shield adjacent wires of a test clip and ribbon cable assembly from each other to avoid signal crosstalk and thereby improve the reliability of the test.